The invention relates to a method for regulating the distance of a vehicle from a preceding vehicle (vehicle ahead).
With vehicles, especially with commercial vehicles, the momentum of the vehicle can be advantageously used to reduce the fuel consumption. For this purpose, in suitable situations an increase in speed or a reduction in speed is carried out. The generally applicable background of said measure is to avoid braking and in return to reduce the length and intensity of a drive phase. Here the momentum of the vehicle is used in a road section lying at the end or start of a drive phase.
Such a utilization of momentum can take place individually by a corresponding driving style of a driver. An improved utilization of momentum is, however, achieved by automation using a driver assistance system in connection with a speed regulation system, e.g. as is known from DE 10 2008 023 135 A1. Relevant situations for a momentum utilization phase are determined in advance with road route information, which is provided in the vehicle by an extended navigation system. Such situations can arise from the topography, for example increasing downhill gradient, end of gradient, tight bend, etc. or from the knowledge of the road infrastructure, for example the start of a village, the start of a speed limit, etc. Furthermore, situations can be derived from the objective of operating the vehicle in relation to the topography and the road infrastructure at an optimal operating point for consumption and wear. Suitable optimizing measures for this purpose are known, for example from DE 10 2008 035 944 B4.
If the speed profile of vehicles that use a saving situation is compared with vehicles travelling at constant speed, depending on the saving situation there is a difference of the speed profiles and hence also a variation of the separation of the vehicles from each other. Therefore, for a full utilization of a saving situation by a vehicle it is necessary that there is sufficient distance to a vehicle ahead. For this purpose a method for the special situation of a build-up of momentum prior to a gradient is already known from DE 10 2006 003 625 A1, with which it is provided that there is such a large distance available ahead that an increased speed necessary for the utilization of momentum does not result in too short a distance to the vehicle ahead. Here an adjustment of the target distance to the vehicle ahead is carried out on the basis of topography information prior to gradients during distance regulation. Specific information, especially how large and how long in advance thereof an additional separation should be built up, is not given here. Particularly the type and manner of the build-up of the additional separation and its length are, however, essential for acceptance of an automated driving mode with a momentum utilization phase, especially in connection with the following traffic and the effects on behaviour in convoy traffic.